According to the National Heart, Lung and Blood Institute, an estimated 4.8 M Americans have congestive heart failure (CHF), a condition in which the heart cannot pump enough blood to meet the need of the other organs of the body. The heart grows too large as a result of congestion in the tissues which also effect the lungs and extremities such as the legs. CHF is a chronic condition and is often the end-stage of cardiac disease. Half of all patients diagnosed with CHF are generally dead within 5 years. The disease is present in about 10% of all persons over 70 years of age and each year there are an estimated 400,000 new cases in the U.S. alone.
Treatment options are limited. Drugs, such as diuretics, ACE inhibitors and digitalis are primary therapy and are used to either expand blood vessels or eliminate access salt and water in the body. For late stage patients, heart transplants are an option but the supply of donor hearts are very limited. American Heart Association (AHA) data puts cost of care for CHF patients at $20B annually in the U.S. Actual dollars could be as high as $30–35B given the overlap with other cardiovascular disease states. Various anecdotal data suggests that the per capita spending in Europe is even higher. Thus, CHF is a highly prevalent, chronic disease, with limited treatment options and a very high cost of care on a global basis.
Addressing the importance of alternative therapies to heart transplants for CHF patients, the clinical unmet need is ever increasing, and rapidly. For patients with late-stage CHF current treatment options are limited. Excluding the use of cardiac assist technologies such as VAD-based systems, the only viable treatment option available today is a heart transplant. In recent years, the number of available donors has stabilized at 2,300 per year. However, with the benefits of better health care, more CHF patients are reaching late-stage status, further increasing the need for transplants. As a result, the gap between the number of available donors and the number of patients on the transplant list have doubled in the last 10 years, reaching close to 5,000 patients in the US alone. But even this figure misrepresents the actual need for late-stage treatment, as the screening criteria for acceptance to the transplant waiting list are immediately disqualifying roughly 50 percent of all patients. Calculations by the American Heart Association show that the actual number of US patients in need of late-stage treatment is about 40,000, only counting those 65 years old or younger.
Ventricular Assist Devices are used to off-load the heart and take over the heart's pumping functions. VAD designs originate from other industrial pump applications. The first generation of VADs comprised ordinary displacement pumps. Since then many techniques have been applied in the design of new VAD systems, such as centrifugal pumps and impeller (turbine) pumps.
VADs are currently used for both acute and chronic cases of heart failure. VADs ensure that the vital organs get sufficient blood flow and allow more time to find a suitable heart donor (bridge-to-transplant), as well as time to build strength and improve the patient's general condition before a transplant. Due to the relatively good portability of many current VAD systems, many patients may be able to return to their homes and even to their jobs while awaiting transplantation. This may drastically improve quality of life and reduce the cost associated with extended hospital stays. Most of the VAD systems currently available are used as bridge-to-transplant systems.
It has also been found that VADs can improve the condition of the diseased heart itself. By off-loading the heart for an extended period the heart can rest and sometimes heal itself. This is often referred to as bridge-to-recovery VADs. The use of VADs for this purpose includes not only CHF patients, but also patient categories such as viral myocarditis patients and cardiogenic shock patients. Cardiogenic shock is currently seen in approximately 4 percent of all post cardiotomy patients. Even though some of the VAD systems available today may be used as bridge-to-recovery VADs, they are all generally designed as bridge-to-transplant systems.
Additionally, many CHF patients are elderly and for other reasons might not qualify for a heart transplant. There are also other CHF patient categories where a heart transplant is deemed in vane. For that purpose, VADs or Total Artificial Hearts (TAHs) might be able to provide a viable alternative. Due to the recent FDA approval of the HeartMate VAD system as a destination therapy for patients not eligible for heart transplants, this is likely to drastically increase the market for VAD systems.
Despite the many advances in VAD technology, current devices generally have the several common shortcomings. VAD devices may be too large for transplantation into patients with smaller frames. This excludes many women and children. Many of today's VAD systems require advanced computerized control systems to regulate the function of the pump. Such VADs are costly and labor intensive to operate, excluding many under developed markets. This may also have prevented VAD systems from finding widespread acceptance and use for extended fields of applications in non-surgical settings, such as cardiogenic shock in the ER, ICU, or PTCA laboratory.